Collapsible ladder



Jan. 25, 1966 G. L. LAVRARD GOLLAPSIBLE LADDER 5 Sheets-Sheet 1 FiledFeb. 24, 1964 INVENTOR. GEORGES LOUIS LAVRARD BY MZMM M Beam AGENTS 5Sheets-Sheet 2 Filed Feb. 24, 1964 FIG. 3

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AGENTS Jan. 25, 1966 G. L. LAVRARD 3,231,045

COLLAPSIBLE LADDER Filed Feb. 24, 1964 5 Sheets-Sheet 5 INVENTO GEORGESLOUIS LAV RD BY Wan M 38am AGE NTS United States Patent 3,231,045COLLAPSIBLE LADDER Georges Louis Lavrard, 36 Ave. dn President Wilson,Chatellerauit (Vienne), France Filed Feb. 24, 1864, Ser. No. 346,747Claims priority, application France, Feb. 26, 1963, 690

12 Claims. (Cl. 182-464) a This invention relates to collapsibleladders, and more particularly to a ladder having several hingedlyconnected sections.

More specifically, this invention is concerned with a modification ofthe ladder disclosed and claimed in my earlier United States Patent No.3,073,414.

A principal object of this invention is the provision of a collapsibleladder the several sections of which are automatically locked when theypivot relative to each other into the operative position in which theirside rails are longitudinally alinged.

' Another object is the provision of a ladder which is very rigid whenin the operative position, yet light enough to be easily transported.

j A further object is the provision of a ladder the several elements ofwhich are connected by form-fitting interengagement, and whichavoids-theuse of stressed soldered,

welded, riveted, or bolted connections.

An additional object is the provision of a locking mechanism for rigidlyholding the ladder sections in their operative position and morespecifically of a locking mechanism which is simple and durable, and.which avoids concentration of stresses on individual ladder elements ortheir. parts. A

With these and other objects in view, the invention in one of itsaspects mainly resides in a ladder whose side rails are constituted bylongitudinal sections of tubular material connected by transverse rungsfThe pairs of longitudinally adjacent sections are connected by hingeseach of which comprises hinge plates respectively fixedly fastenedto thetwo connected sections, and arranged for pivoting movement about a pinwhose axis is transverse of the direction of elongation of the rails. Afirst portion of each, hinge .plate is received. in the cavity of theassociatedrail section, and asecond hinge plate portion projects outsideof thatcavity and is oifset from the first portion in a directiontransverse to the direction of elongation of the rail.

Cooperating abutment faces are provided on the rail sections of eachpair,- and engage each other to limit pivoting movement of the railsections in one direction to the operative position. vStop means in thecavity of one rail section cooperate with a latch member mounted on theprojection portion of a hinge plate which is fastened to the other-railsection of the pair. The latch member is movable on the hinge platetoward and away from a position of engagement with the aforementionedstop means when the two rail sections are in the operative position.When the latch member. engagesthe stop means, it prevents pivotingmovement of the two rail sections in the other direction that is, awayfrom the operative position.v Otherfeatures ,andmany of the attendantadvantages of this invention will bereadily appreciated as the samebecomes better understood by reference to the following detaileddescription when considered in connection with the accompanying drawingsin which:.- FIG. 1 shows a portion of a sectional ladder of theinvention in a perspective view which includes one complete section andportions of the two adjoining sections;

FIG. 2 is a perspective partly sectional end view of one of the, rungsof the-ladder on a larger scale that of FIG.. 1;

FIG. 3 shows a hinge portion of the ladder of FIG. 1 in plan section onthe line lII-lll in FIG. 5;

FIG. 4 shows individual hinge elements of the ladder in plan view; and

FIG. 5 is a sectional elevational view of the hinge portion of FIG. 3taken on the lines VV in FIGS. 1 and 3.

Referring now to the drawing in detail, and initially to FIG. 1, thereis seen a portion of a sectional ladder which mainly consists of twoparallel, longitudinal side rails 1, 2 connected by transverse rungs 3b,30. Three sections 1a, 1b, 1c of the rail 1 and the corresponding rungsand sections of the rail 2 are seen in FIG. 1, but a ladder of theinvention normally consists of substantially more than three sections.

The rail sections are respective portions of a rectangular tube ofextruded aluminum which combines the desired properties of stiffness andlightness. Longitudinally adjacent sections of the rails 1, 2 areconnected by hinges. The hinges of each rail-are identical, and aresymmetrical to the hinges of the other rail. The hinge connecting therail sections 112 and 1c will be described in detail hereinafter, andthe description will be understood to be applicable to all the hinges ofthe ladder.

Each hinge in the rail 1 includes four plates 4, 5, 6, 7 of diecastaluminum, and each hinge in the rail 2 includes four correspondingplates 4, 5, 6', 7. The hinge plates have aligned circular openings inwhich a tubular cylindrical end portion of the associated rung 30provides a hinge pin. Only the beaded rim 22 of the hollow hinge pin isvisible in FIG. 1.

Respective portions of the hinge plates 4, 5 are conformingly receivedin the hollow interior of the rail section 1b, and are fixedly fastenedto the rail section by rivets 15. The hinge, plates 6, 7 are similarlyfastened in the rail section 10 by rivets 16. A flat latch bar 18 ofcease-hardened steel projects outward from a recess between the portionsof the hinge plates 4, 5 which project from the cavity in the railsection 112 are transversely offset thereform. The angularly bent freeend of the bar 18 provides a handle 17. As will become apparenthereinafter the latch bar 18 locks the two adjacent side rail sec-tions1b, 1c in a position in which the sections abuttingly engage each otheralong an interface 18.

Each rung is a section of an extruded aluminum bar whose cross sectionalshape is best seen in FIG. 2. The rung consists of a cylindrical tube 8from which short webs 8, 10 project in opposite radial directions.Flanges 11, 11 are integrally fastened to the respective webs.Theirou-ter faces extend in support planes obliquely inclined relativeto each other, and are almost flat. They are provided with sharp-edgecorrugations i2. Reinforcing ribs 13, 14 on the inner face of eachflange 11, 11' make the flanges stiff enough so that they may serve astreads. The corrugations 12 prevents slipping. The web and flangeportions are removed from the end portions of each rung so that the tube8 projects on either side beyond'the treads of the rung. The tubeprovides the pivot pin for the aforementioned hinged plates.

The hinge structure is better seen in FIG. 3, and details of theindividual hinge plates are most clearly evi dent from FIG. 4. The fourhinge plates 4, 5, 6, 7 are formed with respective circular openings 24,25, 26, 27 in which the tube 8 is coaxially received. The hinge platesare axially secured on the tube 8 between the aforementioned beaded rim22 on the axial end of the tube 8 and the axial end faces of the webs 9,10 and of the flanges 11, 11'. The openings 24, 25 are large enough toaccommodate a tubular nylon washer 20 whichis coaxially arranged on thetube 8 tofacilitate rotation of the plates 4, 5 on the tube 8. Frictionbetween the plates 4, 6 is reduced by a fiat, circular nylon washer 21,and a similar washer is interposed between the plates and 7.

The plate 4 has a recess or groove 23 which slidably receives the latchbar 18 as will become more fully apparent hereinafter from thedescription of FIG. 5. The plate 5 is shaped to conform to the plate 4and to provide a cover for the recess 23. The plates 4, 5 are axiallyinterposed on the tube 8 between the plates 6, 7 the inner faces ofwhich are recessed to receive the plates 4, 5 therebetween.

The outer face of the hingle plate t5 carries two locking abutments 28,29 each of which extends about the tube 8 in a circular arc of almost180, and axially projects from the hinge plate 6. The abutments 28, 29define therebetween two circumferential gaps 30. The abutments 28, 29are received between the flanges 11, 11" of the associated rung 3c inthe assembled condition of the ladder as indicated by the phantom viewof the abutments in FIG. 2, and the gaps 30 receive terminal portions ofthe webs 9, it) therebetween as best seen in FIG.

'3. The abutments when interengaged with elements of the rung 3c preventrotation of the rung relative to the associated rail section 10.

FIG. 5 shows how rotation of the sections 11), 1c relative to each otherabout the axis 36 of the tube 8 is prevented by the latch bar 18. Thebar 18 is curved in a hat, aproxirnately circular arc. It islongitudinally guided in the aforementioned recess 23 of the hinge plate4. The end portion of the bar 18-rernote from the handle 17 has a sideface which abuts against a transverse stop pin 32 secured between theplates 6 and 7 in the rail section is so as to prevent rotation of thesection about the axis 36 of the tube 8 in a clockwise direction, asviewed in FIG. 5. The other side face 31 is obliquely inclined relativeto the direction of elongation of the bar 18.

counterclockwise rotation of the rail section .10 is prevented byabutting engagement of the sections 1b, 10 at the interface 19. Becausethe pin 32 is as far removed from the axis 36 as is possible in astructure of this kind, the stresses on the free end portion 31 duringuse of the ladder are relatively small. They are transmitted by the bar18 to the sturdy hinge plate 4 along relatively large contact areas of aguide face which are indicated in the drawing by double arrows 4t) and41.

The latch bar 13 is urged into the locking position illustrated in FIG.5 by a helical compression spring 34 which is interposed between anintegral transverse web 35 of the hinge plate 5 and an integral lug 33of the latch bar 18. The longitudinal movement of the latch bar islimited by engagement of two abutment faces 37, 38 on a projectingportion of the hinge plate 4 with corresponding faces in a recess 39 ofthe latch bar.

The ladder described hereinabove may be folded or rolled up in a mannerevident from my earlier US. Patent No. 3,073,414. If the ladder is to befolded, the latch bars 18 at the two lateral ends of each rung aresimultaneously pulled outward of the associated hinges to unlock thesame. If only one pair of hinges is unlocked, the two rigid portions ofthe ladder on either side of the unlocked hinges may be set up as a stepladder. The treads 11 of one ladder portion, and the treads 11' of theother portion face upward under such conditions. Because of the obliqueinclination of the treads 11, 11' relative to each other, both portionsof the ladder offer tread surfaces which are horizontal or nearlyhorizontal. If a folded or rolled ladder of the invention isstraightened, the pins 32 cammingly engage the inclined faces 31' of thelatch bars 18, and displace the bars against the pressure of theirsprings 34 until the bars can drop into their locking position shown inFIG. 5.

The ladder of the invention is very rigid in its operative position, yetquite light. The use of tubular rails made of aluminum or similar lightmetal partly accounts for the favorable combination of high mechanicalstrength and low weight. The specific hinge structure of the laddersafely prevents relative movement of the individual rafl sections. Theuse of a latch bar of a material which is very much harder and strongerthan that of the cooperating ladder elements makes the hinge structuredurable and reliable.

The useful life of the latch bar i-s greatly extended by the wide radialspacing of the stop pin 31 relative to the axis 36 from those portionsof the hinge plate 4 to which the latch bar transmits the bendingstresses which would move the rail sections away from their illustratedoperative position. The anchorage of the latch bar is so firm that aladder of the invention may be employed safely in an obliquely inclinedposition with the outwardly projecting portions of the hinge platesdirected toward the person who climbs the ladder.

The ladder is free from solder joints, welded or bolted connections. Therivets 15, 16 merely hold the hinge plates in position, but they are notsubjected to major stresses in the normal use of the ladder. The weightsupported by the ladder is transmitted from rail section to rail sectionby the abutting relatively large faces at the interface 19. The bendingstresses in the ladder are transmitted from the conformingly receivedhinge plate sections to the rail sections. The contact areas betweenhinge plates and rail sections are large, and stress con centrations areavoided.

The beaded rim 22 of the rungs is not normally sub. jected to severestresses. The tube 8 transmits the weight of a person supported on thetread 11 to associated hinge plates which in turn abut against an edgeof the associ atcd rail section. The treads are held in proper positionby interengagement of respective portions of the tread and of anadjacent hinge plate.

A ladder having latch bars in each hinge of both side rails has beenshown in the drawing, and such an arrangement is preferred where theladder is to be subjected to high stresses. In most instances, it issufficient to provide a single lockable hinge on each rung, and lockinghinges are preferably arranged in one rail only. The manner in which thelocking bars 18 are distributed over the several hinges of a ladder maybe selected, however, to suit specific requirements without departingfrom the spirit and scope of this invention.

Obviously, many other modifications and variations of the presentinvention are possible in the light of the above teachings. It is,therefore, to be understood that, within the scope of the appendedclaims, the invention may be practiced otherwise than as specificallydescribed.

What is claimed is:

1. A collapsible ladder comprising, in combination:

(a) two elongated side rails, each side rail being mainly constituted bya plurality of longitudinal'sections of tubular material definingrespective cavities therein, each of said pluralities including a firstsection and a second section jointly constituting a pair oflongitudinally consecutive side rail sections;

(b) a plurality of longitudinally spaced rungs transversely connectingsaid side rails;

(c) first and second hinge plate means respectively fixedly fastened tothe first and second side rail section of each pair;

(d) hinge pin means connecting the first and second plate means of eachpair of side rail sections for pivoting movement of said sections abouta transverse axis;

(e) cooperating abutment means on the side rail sections of each pairfor arresting said pivoting movement in one direction in an operativeposition in which the rail sections of;;said pair are longitudinallyaligned;

(f)' stop pin means mounted in the cavity of the first section of one ofsaid pairs, said stop pin means moving with said first section in anarcuate path when said first section is pivoted about said transverseaxis away from said operative position,

(1) the second hinge plate means of said one pair having a guide face inthe cavity of said first section spaced from said stop pin means in adirection opposite to said one direction when said sections are in saidoperative position; and

(g) latch means mounted on said second hinge plate means for slidingmovement along said guide face toward and away from a position ofengagement in which said latch means is interposed between said stop pinmeans and said guide face for simultaneous engagement with said stop pinmeans and said guide face.

2. A ladder as set forth in claim 1, wherein each hinge plate means hasa first portion received and fixedly fastened in the cavity of theassociated rail section and a second portion outside said cavity, saidhinge pin means pivotally connecting said second portions.

3. A ladder as set forth in claim 1, wherein said hinge pin means issecured to one of said rungs.

4. A ladder as set forth in claim 3, further comprising interengaginglocking means on one of said hinge plate means and on said one rung forpreventing pivoting movement of said rung about said axis relative tosaid one hinge plate means.

5. A ladder as set forth in claim 4, wherein said one rung has asubstantially flat tread face.

6. A ladder as set forth in claim 4, wherein said rung has twosubstantially flat tread faces oppositely spaced from said axis andobliquely inclined relative to each other.

7. A ladder as set forth in claim 1, wherein each of said rungs is aunitary elongated structure having two longitudinally terminal portions,one of said terminal portions constituting said hinge pin means, and aportion intermediate said terminal portions, said intermediate portionhaving a tread face defining a plane of support, the ladder furthercomprising locking means on one of said hinge plate means and engagingsaid rung for preventing pivotal movement of said rung about said axisrelative to said one hinge plate means.

8. A ladder as set forth in claim 7, wherein said rung has a secondtread face defining a second plane of support obliquely inclinedrelative to said first-mentioned plane of support.

9. A ladder as set forth in claim 1, wherein said second hinge platemeans is formed with a recess, and a portion of said latch means isconformingly received in said recess for said sliding movement.

10. A ladder as set forth in claim 9, further comprising handle means ona portion of said latch means outside said recess for actuating saidsliding movement.

11. A ladder as set forth in claim 9, further comprising yieldablyresilient means urging said latch means toward said position ofengagement.

12. A ladder as set forth in claim 11, wherein said latch means has acam face obliquely inclined relative References Cited by the ExaminerUNITED STATES PATENTS 3,073,414 1/1963 Lavrard 18224 X FOREIGN PATENTS921,383 3/1963 Great Britain. 346,989 6/ 1960 Switzerland.

HARRISON R. MOSELEY, Primary Examiner.

REINALDO P. MACHADO, Examiner.

1. A COLLAPSIBLE LADDER COMPRISING, IN COMBINATION: (A) TWO ELONGATEDSIDE RAILS, EACH SIDE RAIL BEING MAINLY CONSTITUTED BY A PLURALITY OFLONGITUDINAL SECTIONS OF TUBULAR MATERIAL DEFINING RESPECTIVE CAVITIESTHEREIN, EACH OF SAID PLURALITIES INCLUDING A FIRST SECTION AND A SECONDSECTION JOINTLY CONSTITUTING A PAIR OF LONGITUDINALLY CONSECUTIVE SIDERAIL SECTIONS; (B) A PLURALITY OF LONGITUDINALLY SPACED RUNGSTRANSVERSLY CONNECTING SAID SIDE RAILS; (C) FIRST AND SECOND HINGE PLATEMEANS RESPECTIVELY FIXEDLY FASTENED TO THE FIRST AND SECOND SIDE RAILSECTON OF EACH PAIR; (D) HINGE PIN MEANS CONNECTING THE FIRST AND SECONDPLATE MEANS OF EACH PAIR OF SIDE RAIL SECTIONS FOR PIOVOTING MOVEMENT OFSAID SECTIONS ABOUT A TRANSVERSE AXIS; (E) COOPERATING ABUTMENT MEANS ONTHE SIDE RAIL SECTIONS OF EACH PAIR FOR ARRESTING SAID PIVOTING MOVEMENTIN ONE DIRECTION IN AN OPERATIVE POSITION IN WHICH THE RAIL SECTIONS OFSAID PAIR ARE LONGITUDINALLY ALIGNED; (F) STOP PIN MEANS MOUNTED IN THECAVITY OF THE FIRST SECTION OF ONE OF SAID PAIRS, SAID STOP PIN MEANSMOVING WITH SAID FIRST SECTION IN AN ARCUATE PATH WHEN SAID FIRSTSECTION IS PIVOTED ABOUT SAID TRANSVERSE AXIS AWAY FROM SAID OPERATIVEPOSITION,